U.S. patent number 11,177,108 [Application Number 16/979,952] was granted by the patent office on 2021-11-16 for charged particle beam application apparatus.
This patent grant is currently assigned to HITACHI HIGH-TECH CORPORATION. The grantee listed for this patent is Hitachi High-Tech Corporation. Invention is credited to Takashi Dobashi, Momoyo Enyama, Akira Ikegami, Yuta Kawamoto, Yasuhiro Shirasaki.
United States Patent |
11,177,108 |
Shirasaki , et al. |
November 16, 2021 |
Charged particle beam application apparatus
Abstract
A charged particle beam application apparatus includes a beam
separator. The beam separator includes a first magnetic pole, a
second magnetic pole facing the first magnetic pole, a first
electrode and a second electrode that extend along an optical axis
of a primary beam and are arranged in a first direction
perpendicular to the optical axis, on a first surface of the first
magnetic pole which faces the second magnetic pole, and a third
electrode and a fourth electrode that extend along the optical axis
and face the first electrode and the second electrode,
respectively, on a second surface of the second magnetic pole which
faces the first magnetic pole.
Inventors: |
Shirasaki; Yasuhiro (Tokyo,
JP), Dobashi; Takashi (Tokyo, JP), Enyama;
Momoyo (Tokyo, JP), Ikegami; Akira (Tokyo,
JP), Kawamoto; Yuta (Tokyo, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Hitachi High-Tech Corporation |
Tokyo |
N/A |
JP |
|
|
Assignee: |
HITACHI HIGH-TECH CORPORATION
(Tokyo, JP)
|
Family
ID: |
1000005933177 |
Appl.
No.: |
16/979,952 |
Filed: |
March 30, 2018 |
PCT
Filed: |
March 30, 2018 |
PCT No.: |
PCT/JP2018/013901 |
371(c)(1),(2),(4) Date: |
September 11, 2020 |
PCT
Pub. No.: |
WO2019/187118 |
PCT
Pub. Date: |
October 03, 2019 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20210005417 A1 |
Jan 7, 2021 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01J
37/244 (20130101); H01J 37/28 (20130101); H01J
37/1475 (20130101) |
Current International
Class: |
H01J
37/147 (20060101); H01J 37/244 (20060101); H01J
37/28 (20060101) |
Field of
Search: |
;250/306,307,310,311,396R,396ML |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
H11233062 |
|
Aug 1999 |
|
JP |
|
2001124713 |
|
May 2001 |
|
JP |
|
2003187730 |
|
Jul 2003 |
|
JP |
|
Other References
Search Report dated Jun. 26, 2018 in International Application No.
PCT/JP2018/013901. cited by applicant .
Written Opinion dated Jun. 26, 2018 in International Application
No. PCT/JP2018/013901. cited by applicant.
|
Primary Examiner: McCormack; Jason L
Attorney, Agent or Firm: Miles & Stockbridge, P.C.
Claims
The invention claimed is:
1. A charged particle beam application apparatus that detects a
secondary beam of charged particles generated by irradiating a
sample with a primary beam of charged particles, the charged
particle beam application apparatus comprising: a primary beam
source that outputs a primary beam for radiating a sample; a beam
separator that generates an internal electromagnetic field so that
the primary beam travels straight, and a trajectory of the primary
beam and a trajectory of the secondary beam are separated; a
control unit that controls a voltage and a current applied to an
electrode and a coil that generate the internal electromagnetic
field of the beam separator; and a detector that detects the
secondary beam from the beam separator, wherein the beam separator
includes: a first magnetic pole; a second magnetic pole facing the
first magnetic pole; a first electrode and a second electrode that
extend along an optical axis of the primary beam and are arranged
in a first direction perpendicular to the optical axis, on a first
surface of the first magnetic pole which faces the second magnetic
pole; and a third electrode and a fourth electrode that extend
along the optical axis and face the first electrode and the second
electrode, respectively, on a second surface of the second magnetic
pole which faces the first magnetic pole.
2. The charged particle beam application apparatus according to
claim 1, wherein a potential applied to the second electrode is
higher than a potential applied to the first electrode, and wherein
a potential applied to the fourth electrode is higher than a
potential applied to the third electrode.
3. The charged particle beam application apparatus according to
claim 1, wherein the beam separator further includes: a third
magnetic pole arranged along the trajectory of the secondary beam
between the first magnetic pole and the detector; and a fourth
magnetic pole facing the third magnetic pole, and wherein the third
magnetic pole and the fourth magnetic pole form an internal
magnetic field that deflects the secondary beam emitted from a
space between the first magnetic pole and the second magnetic pole
in the same direction as a magnetic field of the internal
electromagnetic field.
4. The charged particle beam application apparatus according to
claim 3, wherein a distance along the first direction from an end
of the first magnetic pole on a side of the third magnetic pole to
the optical axis is equal to or more than half a distance between
the first surface of the first magnetic pole and the second surface
of the second magnetic pole.
5. The charged particle beam application apparatus according to
claim 1, further comprising: a fifth electrode and a sixth
electrode that extend along the optical axis and are arranged in
the first direction between the first electrode and the second
electrode, on the first surface; and a seventh electrode and an
eighth electrode that extend along the optical axis and face the
fifth electrode and the sixth electrode, respectively, on the
second surface.
6. The charged particle beam application apparatus according to
claim 5, wherein a potential applied to the sixth electrode is
higher than a potential applied to the fifth electrode and lower
than a potential applied to the second electrode, wherein the
potential applied to the fifth electrode is higher than a potential
applied to the first electrode, wherein a potential applied to the
eighth electrode is higher than a potential applied to the seventh
electrode and lower than a potential applied to the fourth
electrode, and wherein the potential applied to the seventh
electrode is higher than a potential applied to the third
electrode.
7. The charged particle beam application apparatus according to
claim 1, further comprising: a first electrode group which includes
a plurality of electrodes including the first electrode and the
second electrode that are arranged on the first surface in the
first direction and extend along the optical axis, and in which
adjacent electrodes are connected by a resistor; and a second
electrode group which includes a plurality of electrodes including
the third electrode and the fourth electrode that are arranged on
the second surface in the first direction and respectively face the
electrodes of the first electrode group, and in which adjacent
electrodes are connected by a resistor, wherein a voltage is
applied to electrodes at both ends of each of the first electrode
group and the second electrode group.
8. The charged particle beam application apparatus according to
claim 1, further comprising: a sheet-shaped first body portion that
connects between the first electrode and the second electrode and
is formed of a material having a higher resistance value than the
first electrode and the second electrode; and a sheet-shaped second
body portion that connects between the third electrode and the
fourth electrode and is formed of a material having higher
resistance value than the third electrode and the fourth electrode,
wherein a voltage is applied between the first electrode and the
second electrode and a voltage is applied between the third
electrode and the fourth electrode.
9. The charged particle beam application apparatus according to
claim 1, further comprising: an image shift deflector arranged
between the sample and the beam separator; and a swing-back
deflector that is arranged between the image shift deflector and
the beam separator, and swings back the secondary beam to the beam
separator in association with image shift by the image shift
deflector.
10. The charged particle beam application apparatus according to
claim 1, further comprising a secondary optical system between the
beam separator and the detector, wherein the detector includes a
plurality of sensors and is capable of simultaneously detecting a
plurality of secondary beams from the sample.
11. The charged particle beam application apparatus according to
claim 10, further comprising a divider that is arranged between the
primary beam source and the beam separator, and divides the primary
beam from the primary beam source into a plurality of primary
beams.
12. A charged particle beam application apparatus that detects a
secondary beam of charged particles generated by irradiating a
sample with a primary beam of charged particles, the charged
particle beam application apparatus comprising: a primary beam
source that outputs a primary beam for radiating a sample; a beam
separator that includes a first electromagnetic pole unit and a
second electromagnetic pole unit facing each other, and generates
an internal electromagnetic field so that the primary beam travels
straight, and a trajectory of the primary beam and a trajectory of
the secondary beam are separated; and a detector that detects the
secondary beam from the beam separator, wherein the first
electromagnetic pole unit includes a first plate made of a magnetic
material, the first plate extending along an optical axis of the
primary beam, wherein the second electromagnetic pole unit includes
a second plate facing the first plate in a second direction
perpendicular to the optical axis, the second plate being made of a
magnetic material, and extending along the optical axis, wherein a
position of the optical axis in the second direction is between the
first plate and the second plate in the second direction, wherein
the first plate includes first and second magnetic poles on a
surface facing the second plate, wherein the second plate includes
third and fourth magnetic poles facing the first and second
magnetic poles, wherein the first and second magnetic poles extend
along the optical axis and are arranged in a first direction
perpendicular to the optical axis and the second direction, wherein
the third and fourth magnetic poles extend along the optical axis,
are arranged in the first direction, and generate magnetic fields
for the first and second magnetic poles, respectively, wherein a
potential applied to the second magnetic pole is higher than a
potential applied to the first magnetic pole, and wherein a
potential applied to the fourth magnetic pole is higher than a
potential applied to the third magnetic pole.
13. The charged particle beam application apparatus according to
claim 12, further comprising: an image shift deflector arranged
between the sample and the beam separator; and a swing-back
deflector that is arranged between the image shift deflector and
the beam separator, and swings back the secondary beam to the beam
separator in association with image shift by the image shift
deflector.
14. The charged particle beam application apparatus according to
claim 12, further comprising a secondary optical system between the
beam separator and the detector, wherein the detector includes a
plurality of sensors and is capable of simultaneously detecting a
plurality of secondary beams from the sample.
15. The charged particle beam application apparatus according to
claim 14, further comprising a divider that is arranged between the
primary beam source and the beam separator, and divides the primary
beam from the primary beam source into a plurality of primary
beams.
Description
TECHNICAL FIELD
The present disclosure relates to a charged particle beam
application apparatus.
BACKGROUND ART
A charged particle beam application apparatus is used to observe a
fine structure. In a semiconductor manufacturing process, a charged
particle beam application apparatus that uses a charged particle
beam such as an electron beam is used for measuring or inspecting
the size and shape of a semiconductor device. One example is a
scanning electron microscope (SEM). The SEM irradiates a sample to
be observed with an electron beam (hereinafter referred to as a
primary beam) generated from an electron source, detects secondary
electrons generated thereby with a detector, and converts them into
an electric signal, thereby generating an image.
In order to detect the secondary electrons, a beam separator that
separates the trajectory of the secondary electrons (hereinafter
referred to as a secondary beam) from the primary beam is required.
As the beam separator, a magnetic field sector that deflects a beam
in a wide magnetic field region and an ExB that deflects a beam by
an electromagnetic field generated in a local region are known.
Further, for example, PTL 1 discloses a beam separator using an
electric field and a magnetic field.
CITATION LIST
Patent Literature
PTL 1: JP 2003-187730 A
SUMMARY OF INVENTION
Technical Problem
The SEM requires a detection optical system that directly detects
the secondary beam and discriminates a signal of the secondary beam
in order to improve the contrast of the image to be acquired. In
order to arrange the detection optical system without interfering
with the primary beam, a beam separator capable of deflecting the
secondary beam at a large angle is desired.
However, the conventional magnetic field sector can deflect the
secondary beam at a large angle (90 degrees), but it is difficult
to adjust an optical axis because magnetic field sector deflects
the primary beam, that is, because the primary beam is a curved
optical system. Further, the conventional magnetic field sector is
tall and easily interferes with other optical elements. In the ExB,
the control of the primary beam is relatively simple, but the
deflection angle of the secondary beam is small in principle.
Therefore, it is necessary to arrange a secondary optical system
for guiding the secondary beam to the detection optical system and
an optical element arranged upstream of the ExB with respect to the
primary beam with a distance from the ExB. This not only has a
large restriction on the optical conditions, but also increases the
column length of the SEM, which increases the influence of external
vibrations and degrades the resolution of the primary beam.
Solution to Problem
According to one example of the present disclosure, there is
provided a charged particle beam application apparatus that detects
a secondary beam of charged particles generated by irradiating a
sample with a primary beam of charged particles, the charged
particle beam application apparatus including: a primary beam
source that outputs a primary beam for radiating a sample; a beam
separator that generates an internal electromagnetic field so that
the primary beam travels straight, and a trajectory of the primary
beam and a trajectory of the secondary beam are separated; a
control unit that controls a voltage and a current applied to an
electrode and a coil that generate the internal electromagnetic
field of the beam separator; and a detector that detects the
secondary beam from the beam separator, in which the beam separator
includes: a first magnetic pole; a second magnetic pole facing the
first magnetic pole; a first electrode and a second electrode that
extend along an optical axis of the primary beam and are arranged
in a first direction perpendicular to the optical axis, on a first
surface of the first magnetic pole which faces the second magnetic
pole; and a third electrode and a fourth electrode that extend
along the optical axis and face the first electrode and the second
electrode, respectively, on a second surface of the second magnetic
pole which faces the first magnetic pole.
According to another example of the present disclosure, there is
provided a charged particle beam application apparatus that detects
a secondary beam of charged particles generated by irradiating a
sample with a primary beam of charged particles, the charged
particle beam application apparatus including: a primary beam
source that outputs a primary beam for radiating a sample; a beam
separator that includes a first electromagnetic pole unit and a
second electromagnetic pole unit facing each other, and generates
an internal electromagnetic field so that the primary beam travels
straight, and a trajectory of the primary beam and a trajectory of
the secondary beam are separated; and a detector that detects the
secondary beam from the beam separator, in which the first
electromagnetic pole unit includes a first plate made of a magnetic
material, the first plate extending along an optical axis of the
primary beam, in which the second electromagnetic pole unit
includes a second plate facing the first plate in a second
direction perpendicular to the optical axis, the second plate being
made of a magnetic material and extending along the optical axis,
in which a position of the optical axis in the second direction is
between the first plate and the second plate in the second
direction, in which the first plate includes first and second
magnetic poles on a surface facing the second plate, in which the
second plate includes third and fourth magnetic poles facing the
first and second magnetic poles, in which the first and second
magnetic poles extend along the optical axis and are arranged in a
first direction perpendicular to the optical axis and the second
direction, in which the third and fourth magnetic poles extend
along the optical axis, are arranged in the first direction, and
generate magnetic fields for the first and second magnetic poles,
respectively, in which a potential applied to the second magnetic
pole is higher than a potential applied to the first magnetic pole,
and in which a potential applied to the fourth magnetic pole is
higher than a potential applied to the third magnetic pole.
Advantageous Effects of Invention
According to one aspect of the present disclosure, it is possible
to provide a charged particle beam application apparatus in which
the control of the primary beam is simple and the secondary beam is
deflected at a large angle to directly detect the secondary beam
and discriminate a signal of the secondary beam.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a view showing a schematic configuration of an electron
beam observation apparatus according to a first embodiment.
FIG. 2A shows a front view of a beam separator according to the
first embodiment as seen in a direction perpendicular to an optical
axis of a primary beam.
FIG. 2B shows a sectional view taken along the line IIB-IIB in FIG.
2A.
FIG. 2C shows an example of the sizes of magnetic poles in the beam
separator.
FIG. 2D shows a specific configuration example of a secondary
optical system and a detector for discriminating a signal of a
secondary beam.
FIG. 3A shows a front view of a beam separator according to a
second embodiment as seen in the direction perpendicular to the
optical axis of the primary beam.
FIG. 3B shows a sectional view taken along the line IIIB-IIIB in
FIG. 3A.
FIG. 4 shows a configuration example of electrodes connected by
resistors in a beam separator according to the second
embodiment.
FIG. 5A shows another configuration example of forming an electric
field in the beam separator according to the second embodiment.
FIG. 5B shows a top view of the configuration example shown in FIG.
5A.
FIG. 6A shows a front view of a beam separator according to a third
embodiment as seen in the direction perpendicular to the optical
axis of the primary beam.
FIG. 6B is a top view of the beam separator according to the third
embodiment as seen along the optical axis.
FIG. 7 shows a part of a configuration example of an electron beam
observation apparatus according to a fourth embodiment.
FIG. 8 shows a configuration example of a multi-beam electron beam
observation apparatus according to a fifth embodiment.
DESCRIPTION OF EMBODIMENTS
Embodiments will be described below with reference to the drawings.
In all the drawings for explaining the embodiments, the same
elements are denoted by the same reference numerals, and the
repeated description thereof will be omitted. In the following, as
an example of a charged particle beam application apparatus, a
sample observation apparatus (electron microscope) using an
electron beam is shown. However, the effect of the feature of the
present disclosure is not lost even in a measurement apparatus and
an inspection apparatus as well as the apparatus using an ion
beam.
First Embodiment
FIG. 1 is a view showing a schematic configuration of an electron
beam observation apparatus according to a first embodiment, which
is an example of a charged particle beam application apparatus.
First, the apparatus configuration will be described. A beam
separator 103, a scanning deflector 104, and an objective lens 105
are arranged on the trajectory of a primary beam 102 extracted from
an electron source 101 (primary beam source) toward a sample
106.
The sample 106 is placed on a sample transfer stage 107. The
primary beam 102 radiated on the sample 106 interacts with a
substance near the surface of the sample 106 to generate a
secondary beam 109. As optical elements that act on the secondary
beam 109, a secondary optical system 111 that guides the secondary
beam to the detector and a detector 113 are arranged. The secondary
optical system 111 and the detector 113 are arranged outside the
beam separator 103. The configurations of the secondary optical
system 111 and the detector 113 depend on the presence/absence of
signal discrimination of the secondary beam and the type of the
signal in the case of performing discrimination, and a specific
configuration example will be described later.
A diaphragm, a lens, an aligner, a stigmator, and the like may be
added to adjust the current and axis of the electron beam (not
shown). In the present specification, elements such as an electron
source, a lens, an aligner, and a detector that act on a charged
particle beam are collectively referred to as optical elements.
The scanning deflector 104, the objective lens 105, and the
secondary optical system 111 in this embodiment generate a magnetic
field by exciting current applied to a coil of each optical
element, and act on the primary beam 102 or the secondary beam 109
(electron beam). These optical elements may generate an electric
field or a combination of a magnetic field and an electric field to
act on the electron beam.
All the above optical elements are controlled by a system control
unit 114. For example, the system control unit 114 controls the
amount of current and voltage applied to each optical element. A
user can confirm and change the setting of each optical element
using a user terminal 115. The user terminal 115 is a computer with
an input/output device.
A method of acquiring an image of a sample using this apparatus
configuration will be described. The primary beam (electron beam)
102 emitted from the electron source 101 enters the beam separator
103 from an entrance 110A of the beam separator 103. Details of the
structure of the beam separator 103 and the action on the electron
beam will be described later.
The primary beam 102 travels straight in the beam separator 103 and
exits from an entrance 110B of the beam separator 103. The primary
beam 102 emitted from the beam separator 103 passes through the
scanning deflector 104 and the objective lens 105, and then is
focused at a position 112 on the sample 106. The exciting current
of the scanning deflector 104 is controlled by the system control
unit 114 so that the primary beam 102 scans the sample 106.
Since a negative voltage is applied to the sample 106 by a
retarding voltage source 108, the primary beam 102 is decelerated
and then radiated on the sample 106. In this example, the retarding
voltage source 108 applies a negative voltage to the sample 106,
but the applied voltage is not limited and may be 0 kV. The primary
beam 102 radiated on the sample 106 interacts with a substance near
the surface, and reflected electrons and other secondary electrons
are generated depending on the shape and material of the sample. In
this embodiment, these electrons are collectively called secondary
electrons.
Since a negative voltage is applied to the sample 106 by the
retarding voltage source 108, the secondary electrons generated
from the position 112 become the secondary beam 109 which is
accelerated and returns to the trajectory of the primary beam 102.
The secondary beam 109 passes through the objective lens 105 and
the scanning deflector 104, and then enters the beam separator 103
from the entrance 110B of the beam separator 103.
The beam separator 103 is controlled by the system control unit 114
so that the incident secondary beam 109 is deflected by a
predetermined angle.
The secondary beam 109 exits from the beam separator 103 from an
entrance 110C of the beam separator 103. The secondary beam 109
emitted from the beam separator 103 enters the detector 113 via the
secondary optical system 111. The detector 113 detects the
secondary beam 109 and converts it into a detection signal. The
value of the detection signal changes depending on the shape and
material of the sample 106 at the position 112 at which the primary
beam 102 is applied. The system control unit 114 converts each
value of the detection signal into brightness and generates an SEM
image. The user terminal 115 displays the generated SEM image.
Next, a configuration example of the beam separator 103 in this
embodiment will be described with reference to FIGS. 2A and 2B.
FIG. 2A shows a front view of the beam separator 103 as seen from
the front side of the drawing in the direction perpendicular to the
optical axis (traveling direction) of the primary beam 102. In FIG.
2A, a part of the internal structure of the beam separator 103 is
shown by a broken line. FIG. 2B shows a sectional view taken along
the line IIB-IIB in FIG. 2A.
The beam separator 103 includes two plates 251 and 252 which face
each other and are parallel to each other. The plates 251 and 252
are magnetic materials, and are made of, for example, iron, nickel,
or an alloy thereof. In this example, the shapes of the plates 251
and 252 are mirror-symmetrical.
Annular grooves (for example, rectangular annular shapes) that
define magnetic poles 201 to 204, respectively, are formed on the
facing surfaces of the plates 251 and 252. Coils 231 to 234 are
embedded in the annular grooves, respectively, and parts of the
plates 251 and 252 form magnetic poles.
Specifically, as shown in FIG. 2B, the coils 231 and 233 are
embedded in the surface of the plate 251 facing the plate 252. The
portion of the plate 251 that is surrounded (defined) by the coil
231 constitutes the magnetic pole 201. The portion of the plate 251
that is surrounded (defined) by the coil 233 constitutes the
magnetic pole 203.
As shown in FIG. 2A, the magnetic pole 201 and the magnetic pole
203 extend along the optical axis of the primary beam 102 on the
surface of the plate 251, the magnetic pole 201 acts on the primary
beam 102 and the secondary beam 109, and the magnetic pole 203 acts
only on the secondary beam 109.
As shown in FIG. 2B, the coils 232 and 234 are embedded in the
surface of the plate 252 facing the plate 251. The portion of the
plate 252 that is surrounded (defined) by the coil 232 constitutes
the magnetic pole 202. The portion of the plate 252 that is
surrounded (defined) by the coil 234 constitutes the magnetic pole
204.
As shown in FIG. 2A, the magnetic pole 202 and the magnetic pole
204 extend along the optical axis of the primary beam 102 on the
surface of the plate 252, the magnetic pole 202 acts on the primary
beam 102 and the secondary beam 109, and the magnetic pole 204 acts
only on the secondary beam 109.
As shown in FIG. 2B, the magnetic poles 201 and 202 face each
other. The facing surfaces of the magnetic poles 201 and 202 are
parallel. The shapes of the facing surfaces of the magnetic poles
201 and 202 are mirror-symmetrical. Further, the magnetic poles 203
and 204 face each other. The facing surfaces of the magnetic poles
203 and 204 are parallel. The shapes of the facing surfaces of the
magnetic poles 203 and 204 are mirror-symmetrical.
In this embodiment, the shapes of the magnetic poles 201 to 204 in
the front view are rectangular shapes, but the shapes are not
particularly limited, and for example, the magnetic poles 201 to
204 may have a shape other than the rectangular shape in plan
view.
In the beam separator 103, magnetic fields and an electric field
for causing the primary beam 102 to travel straight and deflecting
the secondary beam 109 at a large angle are formed. The magnetic
fields in the beam separator 103 will be described. The magnetic
field is formed between the magnetic poles 201 and 202 by causing
an electric current to flow through the coils 231 and 232. In the
example of FIG. 2B, (the magnetic flux of) the magnetic field is
directed from the magnetic pole 202 to the magnetic pole 201.
Further, the magnetic field is formed between the magnetic poles
203 and 204 by causing an electric current to flow through the
coils 233 and 234. In the example of FIG. 2B, (the magnetic flux
of) the magnetic field is directed from the magnetic pole 204 to
the magnetic pole 203. The system control unit 114 gives an
exciting current to the coils 231 to 234 so as to form the magnetic
fields shown in FIG. 2B. The system control unit 114 can
independently control the magnetic field between the magnetic poles
202 and 201 and the magnetic field between the magnetic poles 204
and 203.
Next, the electric field in the beam separator 103 will be
described. Electrodes 221 and 222 are arranged on the magnetic pole
201. An insulating layer (not shown) is present between the
electrodes 221 and 222 and the magnetic pole 201 to insulate the
magnetic pole 201 from the electrodes 221 and 222. As shown in FIG.
2A, the electrodes 221 and 222 have a strip-shape extending along
the optical axis of the primary beam 102 on the surface of the
magnetic pole 201, and are arranged in the direction perpendicular
to the optical axis of the primary beam 102. In FIG. 2A, the
electrodes 221 and 222 are arranged in the left-right
direction.
Electrodes 223 and 224 are arranged on the magnetic pole 202. An
insulating layer (not shown) is present between the electrodes 223
and 224 and the magnetic pole 202 to insulate the magnetic pole 202
from the electrodes 223 and 224. As shown in FIG. 2A, the
electrodes 223 and 224 have a strip-shape extending along the
optical axis of the primary beam 102 on the surface of the magnetic
pole 202, and are arranged in the direction perpendicular to the
optical axis of the primary beam 102. In FIG. 2A, the electrodes
223 and 224 are arranged in the left-right direction.
In this embodiment, the electrodes 221 and 223 face each other, and
their shapes are mirror-symmetrical. Further, the electrodes 222
and 224 face each other, and their shapes are
mirror-symmetrical.
By applying a voltage to the electrodes 221 to 224, an electric
field is formed between the magnetic poles 201 and 202. In the
example of FIG. 2B, (the electric flux of) the electric field is
directed from the electrodes 222 and 224 to the electrodes 221 and
223. That is, the potentials of the electrodes 222 and 224 are
relatively positive with respect to the potentials of the
electrodes 221 and 223. As a result, orthogonal magnetic and
electric fields are formed in the space between the magnetic poles
201 and 202 near the primary beam 102. By using magnetic materials
for the electrodes 221 to 224, the magnetic resistance between the
magnetic poles 201 and 202 can be reduced, and the exciting current
required for the coils 231 and 232 can be reduced.
The system control unit 114 applies potentials to the electrodes
222 to 224 so that the electric field shown in FIG. 2B is formed.
For example, the potentials applied to the electrodes 222 and 224
are the same, and the potentials applied to the electrodes 221 and
223 are the same. The potentials applied to the electrodes 222 and
224 and the electrodes 221 and 223 may be different.
As shown in FIG. 2A, the primary beam 102 passes through the space
surrounded by the magnetic pole 201, the magnetic pole 202, and the
electrodes 221 to 224 in the beam separator 103. The electric field
and the magnetic field near the primary beam 102 formed between the
magnetic pole 201 and the magnetic pole 202 are orthogonal to each
other, and the directions of the deflection actions exerted on the
primary beam 102 are opposite to each other. The system control
unit 114 controls the currents applied to the coils 231 and 232 and
the voltages applied to the electrodes 221 to 224 so that the
intensities of the deflection actions become the same. That is, the
Wien condition is satisfied, and the primary beam 102 travels
straight in the beam separator 103. This means that the control of
the primary beam is simpler than the conventional magnetic sector
that also deflects the primary beam.
Specifically, the deflection action of the electric field received
by the primary beam acts from left to right in FIG. 2B, and the
deflection action of the magnetic field acts from right to left in
FIG. 2B. The force due to the electric field acts in the direction
perpendicular to the optical axis of the primary beam 102 and along
the facing surfaces of the magnetic poles 201 and 202 (in-plane
direction) from the magnetic poles 201/202 to the magnetic poles
203/204. The force due to the magnetic field acts in the direction
perpendicular to the optical axis of the primary beam 102 and along
the facing surfaces of the magnetic poles 201 and 202 from the
magnetic poles 203/204 to the magnetic poles 201/202.
The secondary beam 109 that has entered the beam separator 103
enters the space surrounded by the magnetic pole 201, the magnetic
pole 202, and the electrodes 221 to 224. The traveling direction of
the secondary beam 109 includes a component in the opposite
direction to the primary beam 102. Therefore, the secondary beam
109 receives a force in the same direction from the electric field
and the magnetic field in the space surrounded by the magnetic pole
201, the magnetic pole 202, and the electrodes 221 to 224.
Specifically, the secondary beam 109 receives the deflecting action
by the electric field which acts from left to right in FIG. 2B and
the deflecting action by the magnetic field. The electric field and
the magnetic field cause the secondary beam 109 to be deflected in
the direction along the surfaces of the magnetic poles 201 and 202
toward the detector 113. In this way, the electromagnetic field
formed by the magnetic pole 201, the magnetic pole 202, and the
electrodes 221 to 224 separates the secondary beam 109 from the
primary beam 102.
The secondary beam 109 deflected by the electromagnetic field exits
from the space between the magnetic poles 201 and 202 and enters
the space between the magnetic poles 203 and 204. The magnetic
poles 203 and 204 generate the magnetic field in the same direction
as the magnetic field generated by the magnetic poles 201 and 202.
FIG. 2A shows a case where the secondary beam 109 passes through
the space between the electrodes 222 and 224, and the secondary
beam 109 is continuously deflected in the regions of the magnetic
poles 201/202 and the magnetic poles 203/204.
However, the secondary beam 109 need not pass through the space
between the electrodes 222 and 224. Further, the present invention
does not lose the effect even when the secondary beam 109 is not
continuously deflected by dividing the magnetic poles 203 and 204
and providing a region having no magnetic field in the beam
separator 103. In order to relax restrictions on optical elements
near the beam separator 103 and reduce resolution deterioration due
to vibration caused by the column length of the SEM, it is
important to make the beam separator 103 that deflects the
secondary beam 109 at a large angle compact and shorten the length
of the primary beam along the optical axis.
As the large angle deflection of the secondary beam 109 in the
compact beam separator 103, a method of further deflecting the
secondary beam 109 in the magnetic field between the magnetic poles
203 and 204 immediately after the secondary beam 109 passes through
the space between the electrodes 222 and 224 and is separated from
the primary beam 102 is effective. To that end, the integral plates
251/252 with the magnetic poles 201/203 and 203/204 are used.
The secondary beam 109 receives the deflecting action which acts
from left to right in FIG. 2B in the space between the magnetic
poles 203 and 204. The magnetic field causes the secondary beam 109
to be deflected at a large angle toward the detector 113 in the
direction along the surfaces of the magnetic poles 203 and 204, and
then the secondary beam 109 exits from the beam separator 103.
FIG. 2C shows an example of the sizes of the magnetic poles in the
beam separator 103. In FIG. 2C, the distance between the magnetic
pole 201 and the magnetic pole 202, more specifically, the distance
between the facing surfaces of the magnetic pole 201 and the
magnetic pole 202 is represented by L1. Furthermore, the distance
between the optical axis of the primary beam 102 and the end of the
magnetic pole 201 or the magnetic pole 202 on the side of the
magnetic pole 203 or the magnetic pole 204 is represented by
L2.
In one example, the distance L2 is equal to or more than half the
distance L1. By satisfying this relationship, the influence of the
magnetic field formed between the magnetic poles 203 and 204 on the
primary beam 102 can be effectively reduced.
In FIGS. 2B and 2C, the distance between the magnetic pole 201 and
the magnetic pole 202 (distance between the facing surfaces) and
the distance between the magnetic pole 203 and the magnetic pole
204 are the same, but even if they are different, the effect of the
invention is not lost. For example, the distance between the
magnetic pole 203 and the magnetic pole 204 may be greater than the
distance between the magnetic pole 201 and the magnetic pole 202.
Further, the magnetic field strengths of the magnetic pole 201 and
the magnetic pole 202 and the magnetic field strength between the
magnetic pole 203 and the magnetic pole 204 are the same or
different. For example, the magnetic field between the magnetic
poles 203 and 204 is stronger than the magnetic fields of the
magnetic poles 201 and 202. The magnetic poles 203 and 204 may be
omitted.
The secondary beam 109 emitted from the beam separator 103 passes
through the secondary optical system 111 and is then detected by
the detector 113. Since the beam separator 103 deflects the
secondary beam at a large angle, the beam separator 103 does not
interfere with the optical elements on the optical axis of the
primary beam 102, and therefore the degree of freedom in arranging
the secondary optical system 111 is high. When the secondary beam
deflection angle of the beam separator 103 is 90 degrees, the
secondary optical system 111 can be arranged near the entrance 110C
of the beam separator 103.
A method of directly detecting the secondary beam and
discriminating the signal in order to improve the contrast of the
SEM image will be described using a specific configuration example
of the secondary optical system 111 and the detector 113 shown in
FIG. 2D. The secondary optical system 111 is composed of a
deflector 262 and a lens 263, and the detector 113 is composed of a
plurality of detectors 264A to 264C.
In this embodiment, an example in which emission angle signal
discrimination of the secondary electrons is performed by detecting
the secondary electrons generated from the sample 106 with
different detectors according to their emission angles will be
described. The secondary beam 109 emitted from the beam separator
103 has a finite spread, and its spatial distribution depends on
the energy and angular distribution of the secondary electrons
emitted from the sample 106. The secondary beam 109 shown in FIG.
2D is composed of secondary beams 261A to 261C emitted from the
sample 106 to the left (not shown), top, and right (not shown) in
FIG. 2A.
The secondary beams 261A to 261C are deflected by the deflector 262
toward the detector 113, and then the lens 263 deflects the
secondary beams 261A to 261C toward the different detectors 264A to
264C. The signal discrimination of the secondary beams is performed
by detecting the secondary beams 261A to 261C with the different
detectors 264A to 264C, respectively. The SEM images generated by
converting the detection signals of the detectors 264A to 264C,
respectively, are displayed on the user terminal 115.
The user terminal 115 displays all the SEM images generated from
the detection signals of the detectors 264A to 264C or the SEM
image selected by the user. By performing the signal discrimination
of the secondary beams, it becomes possible to improve the contrast
due to the emission angles of the secondary electrons emitted from
the sample 106.
The secondary optical system 111 may include an astigmatism
corrector, a multistage lens, and other optical elements. Further,
the optical elements may be omitted. Further, in this embodiment,
the signal discrimination according to the emission angles of the
secondary electrons is performed, but by including an optical
element such as a Wien filter in the secondary optical system 111,
the signal discrimination according to the emission energies of the
secondary electrons can be performed.
The detector 113 shown in FIG. 2D is composed of the three
detectors 264A to 264C, but the effect of the present invention is
not lost even when the number of detectors is three or more or
three or less. Further, the detector array may be one-dimensional
or two-dimensional. It goes without saying that the more the number
of detectors, the more accurate the signal discrimination of
secondary electrons can be made. As described above, it is possible
to realize the electron beam observation apparatus capable of
directly detecting the secondary beam and discriminating the
signal.
Second Embodiment
In the first embodiment, by using the pair of the magnetic poles
201 and 202 and the two pairs of the electrode 221 and the
electrode 222, and the electrode 223 and the electrodes 224, the
electromagnetic field region where the primary beam 102 travels
straight and the secondary beam 109 is deflected is formed in the
beam separator 103. In this case, the region where the electric
field is uniform near the optical axis of the primary beam 102 is
narrow.
When the primary beam 102 passes through the region where the
electric field is non-uniform, the primary beam 102 does not travel
straight in the beam separator 103, which makes it difficult to
control the primary beam 102. Further, aberration is generated in
the primary beam 102, which deteriorates the resolution of the SEM
image. Therefore, if the region where the electric field is uniform
is narrow, it is difficult to adjust the optical axis of the
primary beam 102. Therefore, in this embodiment, an electron beam
observation apparatus in which the uniformity of the electric field
in the beam separator 103 is improved and the accuracy of adjusting
the optical axis of the primary beam 102 is relaxed will be
described.
A second embodiment will be described with reference to FIGS. 3A to
5B. FIGS. 3A and 3B show another configuration example of the beam
separator 103. The apparatus configuration is the same as the
apparatus configuration of the first embodiment except for the beam
separator 103, and thus the description is omitted. FIG. 3A shows a
front view of the beam separator 103 as seen from the front side of
the drawing in the direction perpendicular to the optical axis of
the primary beam 102. FIG. 3B shows a sectional view taken along
the line IIIB-IIIB in FIG. 3A. The beam separator 103 of this
embodiment includes electrodes 225 to 228 in addition to the
configuration of the first embodiment. The electrodes 225 to 228
can generate a more uniform electric field.
The electrodes 225 and 226 are arranged on the magnetic pole 201.
An insulating layer (not shown) is present between the electrodes
225 and 226 and the magnetic pole 201 to insulate the magnetic pole
201 from the electrodes 225 and 226. As shown in FIG. 3A, the
electrodes 225 and 226 extend along the optical axis of the primary
beam 102 on the surface of the magnetic pole 201, and are arranged
in the direction perpendicular to the optical axis of the primary
beam 102. In FIG. 3A, the electrodes 225 and 226 are arranged
between the electrodes 221 and 222. The electrodes 221, 225, 226,
and 222 are arranged in this order in the left-right direction or
in the direction from the optical axis of the primary beam 102
toward the detector 113.
The electrodes 227 and 228 are arranged on the magnetic pole 202.
An insulating layer (not shown) is present between the electrodes
227 and 228 and the magnetic pole 202 to insulate the magnetic pole
202 from the electrodes 227 and 228. As shown in FIG. 3A, the
electrodes 227 and 228 extend along the optical axis of the primary
beam 102 on the surface of the magnetic pole 202, and are arranged
in the direction perpendicular to the optical axis of the primary
beam 102. In FIG. 3A, the electrodes 227 and 228 are arranged
between the electrodes 223 and 224. In FIG. 3A, the electrodes 223,
227, 228, and 224 are arranged in this order in the left-right
direction or in the direction from the optical axis of the primary
beam 102 toward the detector 113.
In this embodiment, the electrodes 225 and 227 face each other, and
their shapes are mirror-symmetrical. The electrodes 226 and 228
face each other, and their shapes are mirror-symmetrical. In this
embodiment, the electrodes 221 to 228 have the same shape. The
shapes of the electrodes 221 to 228 may be different, and the
positions of the electrodes 225 and 227 and the electrodes 226 and
228 in the left-right direction in FIG. 2B may be different.
An electric field is formed by the electrodes 221 to 228. In the
example of FIG. 3B, the electric field is directed from the
electrodes 222 and 224 in the direction toward the electrodes 221
and 223. The potential applied to the electrode 226 is smaller than
the potential applied to the electrode 222, the potential applied
to the electrode 225 is smaller than the potential applied to the
electrode 226, and the potential applied to the electrode 221 is
smaller than the potential applied to the electrode 225.
The potential applied to the electrode 228 is smaller than the
potential applied to the electrode 224, the potential applied to
the electrode 227 is smaller than the potential applied to the
electrode 228, and the potential applied to the electrode 223 is
smaller than the potential applied to the electrode 227.
In this embodiment, the potentials applied to the electrodes 221
and 223 are the same, the potentials applied to the electrodes 225
and 227 are the same, the potentials applied to the electrodes 226
and 228 are the same, and the potentials applied to electrodes 222
and 224 are the same. The potentials applied to the electrodes of
each of these electrode pairs may be different.
Also in this configuration example, in the region where the primary
beam 102 passes, the electric field formed by the electrodes 221 to
228 and the magnetic field formed by the magnetic poles 201 and 202
are orthogonal to each other, and further, the Wien condition is
satisfied. By increasing the number of electrodes arranged on the
magnetic poles and adjusting the voltage applied to each electrode,
the Wien condition for the primary beam 102 can be satisfied and at
the same time, the uniformity of the electric field formed in the
beam separator 103 can be improved.
In this embodiment, a uniform electric field in which the four
pairs of electrodes composed of the electrodes 221, 225, 226, and
222 and the electrodes 223, 227, 228, and 224 facing them are
orthogonal to the magnetic field between magnetic poles 201 and 202
is formed. By further increasing the number of electrode pairs and
adjusting the voltage of each electrode to expand the region where
the electric field is uniform, the accuracy of adjusting the
optical axis of the primary beam 102 can be further relaxed.
A predetermined voltage is applied to each of the electrodes 221 to
228 by a power supply circuit of the system control unit 114.
Therefore, the same number of voltage power supplies as the number
of electrodes are required. Unlike this, there may be adopted a
configuration in which the electrodes arranged on the same magnetic
pole may be connected by resistors, and a voltage may be applied
only to the electrodes at both ends. FIG. 4 shows a configuration
example of the electrodes 221 to 228 connected by resistors.
Adjacent electrodes of the electrodes 221, 225, 226, and 222 are
connected by resistors 401 to 403. Adjacent electrodes of the
electrodes 223, 227, 228, and 224 are connected by resistors 404 to
406.
The system control unit 114 applies predetermined voltages from the
power supply circuit to the electrodes 221 and 222, and further
applies predetermined voltages from the power supply circuit to the
electrodes 223 and 224. The voltages of the electrodes 221, 225,
226, and 222 are determined by the resistance values of the
electrodes 221 and 222 and the resistors 401 to 403. Similarly, the
voltages of the electrodes 223, 227, 228, and 224 are determined by
the resistance values of the electrodes 223 and 224 and the
resistors 404 to 406. By adjusting the resistance values of the
resistors 401 to 406, the voltages of the electrodes 225 to 228 are
adjusted to form a uniform electric field between the magnetic
poles 201 and 202.
For example, the resistance values of the resistors 401, 402, and
403 are the same as the resistance values of the resistors 404,
405, and 406, respectively. The system control unit 114 applies the
same potential to the electrodes 221 and 223, and applies the same
potential to the electrodes 222 and 224. From the above, by using
the resistors 401 to 406, it is possible to generate a uniform
electric field with a number of voltage power supplies smaller than
the number of electrodes.
FIGS. 5A and 5B show another configuration example for generating
an electric field. The beam separator 103 includes, in addition to
the configuration of the first embodiment described with reference
to FIGS. 2A and 2B, a body portion 501 formed of a sheet-shaped
semiconductive material having a high resistance value that
connects the electrodes 221 and 222, for example, a semiconductor
such as silicon or a semiconductive insulator, and a body portion
502 formed of a sheet-shaped semiconductive material that connects
the electrodes 223 and 224.
When voltages are applied to the electrodes 221 to 224, currents
flow in the body portions 501 and 502. When there is a voltage
difference of 1,000V or more between the electrodes 221 and 222 or
between the electrodes 223 and 224, in order to reduce the loads of
the power supplies in the system control unit 114, it is desirable
to use the body portions 501 and 502 having a resistance value of 1
Mohm or more to reduce the current flowing therethrough.
FIG. 5A shows a plan view of structure arranged on the magnetic
poles 201 and 202 as seen from the optical axis of the primary beam
102 in the direction perpendicular to the optical axis. FIG. 5B
shows a top view of the structure arranged on the magnetic poles
201 and 202 as seen in the direction along the optical axis.
The body portions 501 and 502 have a sheet shape and spread along
the surfaces of the magnetic poles 201 and 202 in the directions
perpendicular to and parallel to the optical axis of the primary
beam 102. In the example shown in FIGS. 5A and 5B, the lengths of
the body portions 501 and 502 in the direction parallel to the
optical axis are the same as those of the electrodes 221 to 224.
The electrodes 221 and 222 are in contact with both ends of the
body portion 501 between the body portion 501 and the magnetic pole
201. The electrodes 223 and 224 are in contact with both ends of
the body portion 502 between the body portion 502 and the magnetic
pole 202.
The system control unit 114 applies a predetermined potential to
each of the electrodes 221 to 224, as in the first embodiment. The
potential of the body portion 501 continuously changes between the
electrodes 221 and 222. Specifically, the potential decreases from
the potential applied to the electrode 222 to the potential applied
to the electrode 221 from the electrode 222 toward the electrode
221. Similarly, the potential of the body portion 502 decreases
from the potential applied to the electrode 224 to the potential
applied to the electrode 223 from the electrode 224 toward the
electrode 223.
In this way, the potentials of the body portions 501 and 502
continuously change, so that a more uniform electric field can be
generated. In the above example, the electrodes are arranged
between the body portion and the surface of the magnetic pole, but
the body portion may be arranged between the electrodes and the
surface of the magnetic pole. The electrode configuration using the
resistors or the body portions shown in FIGS. 4, 5A and 5B for
improving the uniformity of the electric field is not limited to
the beam separator. The electrode configuration shown above can be
used in a deflector that deflects a charged particle beam by an
electric field.
For example, in the case of the electrode configuration of the
deflector using the body portions 501 and 502, in the space between
the body portions 501 and 502, an electric field is generated
according to the voltage difference between the electrodes 221/223
and 222/224 in a direction perpendicular to the optical axis of the
primary beam 102 and a direction parallel to the body portions
501/502. In addition, an electric field is generated according to
the voltage difference between the electrodes 221/222 and 223/224
in the direction perpendicular to the optical axis of the primary
beam 102 and a direction perpendicular to the body portions
501/502. Therefore, the primary beam 102 can be deflected by
adjusting the voltages of the electrodes 221 to 224.
As described above, it is possible to realize the electron beam
observation apparatus in which the uniformity of the electric field
in the beam separator 103 is improved and the accuracy of adjusting
the optical axis of the primary beam 102 is relaxed.
Third Embodiment
In the first embodiment, by using the magnetic poles 201 and 202
and the electrodes 221 to 224, the electromagnetic field region
where the primary beam 102 travels straight and the secondary beam
109 is deflected is formed in the beam separator 103. In this case,
it is necessary to accurately arrange the electrodes 221 to 224 on
the magnetic pole 201 and the magnetic pole 202. Therefore, in this
embodiment, an electron beam observing apparatus will be described
in which a predetermined voltage is applied to each magnetic pole
so that the magnetic poles also function as electrodes, thereby
eliminating the need for arranging electrodes on the magnetic
poles.
Another configuration example of the beam separator 103 will be
described with reference to FIGS. 6A and 6B. The apparatus
configuration is the same as the apparatus configuration of the
first embodiment except for the beam separator 103, and thus the
description is omitted. FIG. 6A shows a front view of the beam
separator 103 as seen from the front side of the drawing in the
direction perpendicular to the optical axis of the primary beam
102. FIG. 6B shows a top view of the beam separator 103 as seen
along the optical axis. The beam separator 103 includes parallel
plates 601 and 603 facing each other and parallel plates 602 and
604 facing each other, in a direction perpendicular to the optical
axis of the primary beam 102. The plates 601 to 604 are magnetic
materials.
The plates 601 and 602 are arranged so as to be perpendicular to
the optical axis of the primary beam 102 and are spaced apart in a
direction perpendicular to the direction in which the plates 601
and 603 or the plates 602 and 604 face each other. The plates 603
and 604 are arranged apart from each other in the same direction as
the arrangement direction of the plates 601 and 602.
Coils (not shown) are embedded in the facing surfaces of the plates
601 and 603, and a part of each of the plates 601 and 603
constitutes a magnetic pole. Similarly, coils (not shown) are
embedded in the facing surfaces of the plates 602 and 604, and a
part of each of the plates 602 and 604 constitutes a magnetic pole.
For example, a rectangular annular coil is embedded along the outer
periphery of the plate. The plates 601 and 602 are fixed by a plate
621 made of an insulator. Similarly, the plates 603 and 604 are
fixed by a plate 622 made of an insulator.
The plates 601 and 603 are connected by pillars 611 and 612 which
act as return paths for the magnetic field. The pillars 611 and 612
are coupled to the upper and lower corners of the plates 601 and
603 on the outer sides, and are spaced apart from each other in the
direction along the optical axis. Similarly, the plates 602 and 604
are connected by pillars 613 and 614. The pillars 613 and 614 are
coupled to the upper and lower corners of the plates 602 and 604 on
the outer sides, and are spaced apart from each other in the
direction along the optical axis.
As shown in FIG. 6B, the beam separator 103 forms therein a
magnetic field directed from the plate 603 to the plate 601 and a
magnetic field directed from the plate 604 to the plate 602. Even
in the space surrounded by the four plates 601 to 604, a magnetic
field including a magnetic field directed from the plate 603 to the
plate 601 and a magnetic field directed from the plate 604 to the
plate 602 is formed.
The magnetic field directed from the plate 604 to the plate 602
returns to the plate 604 through the pillars 613 and 614.
Similarly, the magnetic field directed from the plate 603 to the
plate 601 returns to the plate 603 through the pillars 611 and 612.
Note that, also in a beam separator 103 of another embodiment, the
facing plates may be connected by pillars.
The system control unit 114 applies a predetermined potential to
each of the plates 601 to 604 and causes them to function as
electrodes. In the example shown in FIGS. 6A and 6B, the same
potential is applied to the plates 601 and 603, and the same
potential is applied to the plates 602 and 604. The potentials to
the plates 601 and 603 are lower than the potentials to the plates
602 and 604. Therefore, in the beam separator 103, electric fields
directed from the plates 602 and 604 to the plates 601 and 603 are
formed.
As shown in FIG. 6B, the electric fields and the magnetic fields
orthogonal to each other are formed in the space surrounded by the
four plates 601 to 604. The system control unit 114 applies
voltages to the plates 601 to 604 so that the Wien condition is
satisfied in the region where the primary beam 102 passes in the
beam separator 103, and causes currents to flow through the coils
embedded in the plates 601 to 604. Therefore, the primary beam 102
can travel straight in the beam separator 103.
The secondary beam 109 enters the space surrounded by the four
plates 601 to 604 and is deflected by receiving the force from the
magnetic fields and the electric fields. Specifically, the
secondary beam 109 is deflected in the direction from left to right
in FIGS. 6A and 6B and enters the space interposed between the
plates 602 and 604. The secondary beam 109 receives the force due
to the magnetic fields in the space and is further deflected
largely in the same direction. The secondary beam 109 travels to
the outside from the space interposed between the plates 602 and
604 toward the detector 113. The beam separator 103 in this
embodiment does not include magnetic poles acting only on the
secondary beam 109, but the magnetic poles may be provided in the
same manner as in the first embodiment. Further, the electron beam
may be controlled by eight magnetic poles as in the case of
providing the eight electrodes in FIG. 3B.
As described above, it is possible to realize the electron beam
observing apparatus that separates the secondary beam 109 from the
primary beam 102 at a large angle by using the beam separator 103
that does not require the arrangement of electrodes on the magnetic
poles.
Fourth Embodiment
In the first embodiment, the region where the primary beam 102 is
scanned on the sample 106 by the scanning deflector 104 corresponds
to the field of view of the SEM image. On the other hand, in order
to move the observation field of view, it is effective to deflect
the primary beam with a deflector using an electric field or a
magnetic field to move the irradiation position on the sample
(hereinafter referred to as image shift).
However, as a result, the trajectory of the secondary beam 109
changes, and the incident condition on the beam separator 103 also
changes. In the beam separator 103 that deflects the secondary beam
109 at a large angle, since the flight distance in the beam
separator is long, the secondary beam collides with the magnetic
poles and the electrodes in the beam separator 103 when the
incident condition changes. Therefore, in this embodiment, an
electron beam observation apparatus will be described in which the
trajectory of the secondary beam 109 is corrected in association
with image shift so as not to collide with the magnetic poles and
the electrodes.
A fourth embodiment will be described with reference to FIG. 7.
FIG. 7 shows a part of a configuration example of the electron beam
observation apparatus. The electron beam observation apparatus of
this embodiment further includes an image shift deflector 701 and a
secondary beam swing-back deflector 702 in addition to the
configuration described with reference to FIGS. 2A and 2B.
The image shift deflector 701 is arranged between the beam
separator 103 and the scanning deflector 104. The image shift
deflector 701 deflects the primary beam 102 to change an
irradiation position 112 of the primary beam 102 on the sample 106.
As a result, the observation region of the sample 106 can be
changed without moving the sample transfer stage 107.
The secondary beam swing-back deflector 702 is arranged between the
image shift deflector 701 and the beam separator 103. The secondary
beam swing-back deflector 702 is arranged upstream of the beam
separator 103 as seen from the secondary beam 109, and swings back
the secondary beam 109 to the beam separator 103 in association
with image shift. Accordingly, the secondary beam 109 can be
appropriately detected by the detector 113 regardless of the image
shift amount. The arrangement relationship between the image shift
701 and the secondary beam swing-back deflector 702 may be
reversed.
The operation of the charged particle beam application apparatus
will be described below. Differences from the first embodiment will
be mainly described. The primary beam 102 exits from the beam
separator 103 and passes through the secondary beam swing-back
deflector 702 and the image shift deflector 701. The exciting
current of the image shift deflector 701 is controlled by the
system control unit 114 so that the primary beam 102 is deflected
at a predetermined angle.
The primary beam 102 is focused on the sample 106 after passing
through the scanning deflector 104 and the objective lens 105. The
exciting current of the scanning deflector 104 is controlled by the
system control unit 114 so as to move the primary beam 102 on the
sample 106 for scanning. Further, since a negative voltage is
applied to the sample 106 by the retarding voltage source 108, the
primary beam 102 is decelerated and then radiated on the sample
106.
Secondary electrons generated from the irradiation position of the
primary beam 102 on the sample 106 are accelerated by the negative
voltage from the retarding voltage source 108 to form the secondary
beam 109. The secondary beam 109 passes through the objective lens
105, the scanning deflector 104, and the image shift deflector 701.
The secondary beam 109 is deflected as it passes through the
secondary beam swing-back deflector 702. The secondary beam 109
enters the beam separator 103 from the entrance 110B, exits from
the entrance 110C, passes through the secondary optical system 111,
and is detected by the detector 113.
The secondary beam swing-back deflector 702 is controlled by the
system control unit 114 so that the incident position of the
secondary beam 109 on the beam separator 103 approaches the
incident position when the image shift deflector 701 is off, for
example. For example, the secondary beam swing-back deflector 702
deflects the secondary beam 109 so that the two incident positions
match.
In this way, the secondary beam swing-back deflector 702 deflects
the secondary beam 109 so as to approach the condition of incidence
on the beam separator 103 when the image shift deflector 701 is
off. The amount of deflection (amount of swinging back) by the
secondary beam swing-back deflector 702 is a vector amount, and
depends on the amount of deflection (image shift amount) by the
image shift deflector 701.
The secondary beam swing-back deflector 702 may deflect, when the
image shift deflector 701 is on, the secondary beam 109 so that a
value of an incident condition other than the incident position on
the beam separator 103 approaches a value of the incident condition
when the image shift deflector 701 is off. For example, the
secondary beam swing-back deflector 702 may deflect, when the image
shift deflector 701 is on, the secondary beam 109 so that the
incident angle on the beam separator 103 matches the case that the
image shift deflector 701 is on.
By controlling the secondary beam swing-back deflector 702 so that
the difference in the incident condition of the secondary beam to
the beam separator 103 is small between that when the image shift
deflector 701 is on and that when the image shift deflector 701 is
off, the adverse effect on the detection of the secondary beam due
to the image shift can be reduced.
The detector 113 detects the secondary beam 109. Therefore, in the
electron beam observation apparatus, the system control unit 114
controls the amount of deflection by the secondary beam swing-back
deflector 702 in accordance with the amount of deflection by the
image shift deflector 701, so that the secondary electron signal
can be properly detected by the detector 113 at any image shift
amount.
As described above, it is possible to realize the electron beam
observation apparatus that corrects the trajectory of the secondary
beam 109 in association with image shift so as not to collide with
the magnetic poles of the beam separator 103.
Fifth Embodiment
In the first to fourth embodiments, only one primary beam is
applied to the sample 106, and it takes time to perform observation
in a wide field of view. In this case, when the sample 106 is
observed simultaneously with a plurality of primary beams, the
observation time can be shortened by the number of primary beams.
Therefore, in this embodiment, a multi-beam electron beam
observation apparatus that irradiates a sample with two or more
primary beams will be described. A fifth embodiment will be
described with reference to FIG. 8. FIG. 8 shows a configuration
example of the electron beam observation apparatus. The beam
separator 103 of the present disclosure can also be applied to a
multi-beam electron beam observation apparatus. In FIG. 8, some of
the components, such as the objective lens, are omitted for ease of
explanation.
An example of the multi-beam electron beam observation apparatus
will be described. A condenser lens 803, an aperture array 804, and
a lens array 805 are arranged between the electron source 101 and
the beam separator 103. The condenser lens 803 collimates the
primary beam from the electron source 101 so as to be substantially
parallel. The aperture array 804 is a substrate having apertures
arranged in one dimension or two dimensions, and divides the
primary beam from the condenser lens 803 into a plurality of
primary beams. The aperture array 804 and the lens array 805 are
dividers that divide the primary beam.
In the example of FIG. 8, the aperture array 804 has five
apertures, and the primary beam from the electron source 101 is
divided into five primary beams 102A to 102E. Although the example
in which the number of primary beams is five has been described in
this embodiment, the effect of the present invention is not lost
even if the number of primary beams is more or less than this.
Further, in this embodiment, the method of generating the primary
beams 102A to 102E by dividing the primary beam 102 generated by
the single electron source 101 has been described. However, even
when the primary beams 102A to 102E are generated by using a
plurality of electron sources, the present invention does not lose
its effect.
The divided primary beams 102A to 102E are individually focused by
the lens array 805. The primary beams 102A to 102E individually
focused by the lens array 805 pass through the beam separator 103.
In this embodiment, the electromagnetic field in the beam separator
103 is set so that the primary beams 102A to 102E travel
straight.
After being emitted from the beam separator 103, the primary beams
101A to 101E are deflected by the scanning deflector 104 controlled
by the system control unit 114, and scan the sample 106.
Secondary electrons generated from irradiation positions of the
primary beams 102A to 102E on the sample 106 form secondary beams
109A to 109E.
The beam separator 103 deflects the secondary beams 109A to 109E
and separates their trajectories from the trajectories of the
primary beams 102A to 102E. The configuration of the beam separator
103 and the actions on the primary beams 102A to 102E and the
secondary beams 109A to 109E are as described in the other
embodiments. An electrostatic lens 806 focuses the secondary beams
109A to 109E, respectively, so that the secondary beams 109A to
109E reach the detector 808 without being mixed with each other and
are detected independently.
A swing-back deflector 807 deflects the secondary beams 109A to
109E from the electrostatic lens 806. The positions at which the
secondary beams are generated on the sample 106 change in
synchronization with scanning, and the deflecting action of the
scanning deflector 104 is received at the positions. The system
control unit 114 controls the swing-back deflector 807 in
synchronization with the scanning deflector 104 so that each
secondary beam generated by each primary beam reaches a certain
position on the detector 808 regardless of the scanning of the
primary beam.
From the above, it is possible to realize the multi-beam electron
beam observation apparatus that shortens the observation time in a
wide field of view.
The beam separator of the present disclosure can be applied to an
electron beam observation apparatus of a type different from the
SEM. For example, the beam separator can be applied to low energy
electron microscopy (LEEM).
The present invention is not limited to the embodiments described
above, but includes various modifications. For example, the
embodiments described above have been described in detail for easy
understanding of the present invention, and are not necessarily
limited to those having all the configurations described. Further,
a part of the configuration of one embodiment can be replaced with
the configuration of another embodiment, and further, the
configuration of one embodiment can be added to the configuration
of another embodiment. In addition, it is possible to add, delete,
and replace other configurations for a part of the configuration of
each embodiment.
Each of the above-described configurations, functions, processing
units, and the like may be realized by hardware by designing a part
or all of them with, for example, an integrated circuit. Further,
each of the above-described configurations, functions, and the like
may be realized by software by interpreting and executing a program
that realizes each function by a processor. Information such as a
program, table, and file that realizes each function can be stored
in a recording device such as a memory, hard disk, or SSD (Solid
State Drive), or a recording medium such as an IC card or SD card.
Further, only the control lines or information lines that are
considered necessary for explanation are given, and all the control
lines or information lines are not necessarily given for the
product. Actually, it may be considered that almost all the
components are connected to each other.
* * * * *